A cave family called the Croods survives a natural disaster, due to the overprotective nature of their stubborn patriarch Grug. The only one who questions the family’s sheltered life is his teenaged daughter Eep, who frequently disobeys her father’s orders out of curiosity, which he finds dangerous. The family spend time sheltered in their cave.
One night, while her family is asleep, Eep sneaks out when she sees what she discovers to be a torch of fire, and she encounters an inventive modern human boy named Guy and his pet sloth Belt. He warns her of an impending apocalypse and offers to take her with him, but concerned for her family, Eep stays, getting a shell horn from him to blow in case she needs his help. Reuniting with her frantic family, Eep tries to tell them what Guy told her, but fearing things that are “different” and “new”, they destroy her horn.
A massive earthquake then destroys their home, and to avoid carnivores and omnivores, they descend into a tropical forest that lay hidden behind their cave all the time. Encountering a “Macawnivore”, a brightly colored feline who is afraid of the dark that Eep’s grandmother Gran dubs “Chunky”, the family flees him until he is scared off by swarms of piranhakeets that devour a ground whale. Using another horn, Eep calls to Guy who rescues them from the birds with his fire. After a great deal of confusion regarding their first contact with fire, Grug imprisons Guy in a log until he can guide them somewhere safe. Guy suggests the Croods go to a mountain where there are caves because the Crood family desires a cave. Grug refuses at first, but he decides to go with the promise of a cave. The other Croods were worried that they would get tired and bicker, but Grug doesn’t listen.
When Grug finds a bird, he decides to hunt its egg for dinner. Eep also wants to hunt the egg, but as she’s grounded, she gets replaced by her younger brother Thunk, who is too tired to hunt it. Grug and Thunk fail to capture the bird’s egg, so they get a scorpion instead. During a fight between Thunk and Gran, Eep notices Guy moving away and stops him. Guy wants Eep to stop, so he asks her hunt with him. Eep goes with Guy to hunt, while the others fight among themselves.
Eep and Guy make a trap in order to capture the bird but fail when the two get tangled up, and the bird doesn’t step in the trap. The bird captures the puppet with Guy in it and throws him up in the sky until he lands on the log. Grug asks Guy where Eep is, and he finds her being chased by the bird. Grug gets angry but doesn’t notice that he was about to step on the trap, so Eep pushes him out to save her father. The bird steps on the trap and is thrown up in the sky until it crash-lands on the ground.
The Croods cook the bird, and Guy is tied up with a root chain on his left leg. After dinner, Grug tells them a story, which is based on a true story, about a tiger who is similar to Eep and embarrasses Eep. Guy says that his stories never end up like Grug’s stories, so the Croods decide to listen to Guy’s story much to their interest. Guy tells them about a tiger who flew into a place with more suns in the sky called “Tomorrow”. Guy also tells them stories of “Tomorrow”, a heaven of safety where he is headed and in which curiosity is not deadly as Grug has claimed.
Outrunning the destruction, Guy is trusted enough to be let out of the log, and he gives the Croods rudimentary shoes to walk over the harsh landscape as he leads them to a mountain in which he says will be safe. After the family is split up in a labyrinth of tunnels, all but Grug manage to escape by coming up with ideas of overcoming obstacles in their paths. At his treetop home, Grug sees the impression Guy is leaving on his family, and he becomes jealous, especially when he realizes that Eep has fallen in love with Guy. Attempting to invent things like Guy, Grug only further embarrasses himself and drives his family further away from him.
Reaching the mountain, Grug tries to force his family to hide out in a cave, but they resist, telling him that they can’t live in caves anymore, that they don’t want to survive but to live. This enrages Grug, who places blame on Guy and tries to beat the answer out of him, but they both end up in a tar flow where Grug learns that Guy’s family had perished in one. Touched by that tragic story, Grug has a change of heart and realizes that Guy’s method of survival is better for his family, and so decides to work with him, and they lure Chunky into a trap to free themselves. The family reunites, then flees a massive cataclysm as the land begins to violently rip apart.
The family is cut off from their destination by a continental split, but Grug, realizing the errors of his ways, decides to throw his family to safety. He shares an invention he calls a “hug” with Eep, briefly before sending her across as well. Cut off from his family, Grug finds a cave for safety, where he encounters Chunky, who is truly a frightened and sweet feline, and he comes up with an idea to getting them across the chasm. Using a ribcage and the Piranhakeets to fashion a simple airship, Grug manages to send themselves, and several animals the family had encountered during their journey, across the chasm, reuniting with his family once again. He apologizes to them all and promises to never be so overbearing again.
Later, the Croods have settled on a vast beach, where every day they can follow the light to “Tomorrow”.